In this type of circuit-breaker, it is common practice to provide means for striking a secondary arc having the effect of heating gas in a determined volume or chamber. The resulting increase in temperature causes the pressure to increase in the volume under consideration and this increase in pressure is used either to produce an auxiliary blast or a second blast on the arc, or to assist in the circuit-breaker opening operation, thereby reducing the power required for controlling the circuit-breaker, or else to provide both of these results simultaneously.
Although this technique presents advantages enabling the above-mentioned objectives to be achieved, it nevertheless suffers from drawbacks. It is always damaging to strike arcs since they necessarily wear away certain parts and these parts must therefore be replaced periodically. In addition, arcs give rise to decomposition products of the insulating gas and these products reduce its dielectric qualities.
An object of the present invention is to provide a circuit-breaker in which a given volume is subjected to heating while the circuit-breaker opens, with the effects of the heating being used to improve the performance of the apparatus, but without requiring a secondary arc to be struck.